WO1999053359A1 - Apparatus for displaying an image suspended in space - Google Patents

Apparatus for displaying an image suspended in space Download PDF

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Publication number
WO1999053359A1
WO1999053359A1 PCT/GB1999/000864 GB9900864W WO9953359A1 WO 1999053359 A1 WO1999053359 A1 WO 1999053359A1 GB 9900864 W GB9900864 W GB 9900864W WO 9953359 A1 WO9953359 A1 WO 9953359A1
Authority
WO
WIPO (PCT)
Prior art keywords
retroreflector
light
beamsplitter
concave mirror
reflected
Prior art date
Application number
PCT/GB1999/000864
Other languages
French (fr)
Inventor
John Holden
Original Assignee
Central Research Laboratories Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Central Research Laboratories Limited filed Critical Central Research Laboratories Limited
Priority to EP99910549A priority Critical patent/EP1068554B1/en
Priority to US09/647,889 priority patent/US6421182B1/en
Priority to CA002327412A priority patent/CA2327412A1/en
Priority to DE69900470T priority patent/DE69900470T2/en
Priority to JP2000543866A priority patent/JP2002511601A/en
Publication of WO1999053359A1 publication Critical patent/WO1999053359A1/en

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
    • G02B30/50—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images the image being built up from image elements distributed over a 3D volume, e.g. voxels
    • G02B30/56—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images the image being built up from image elements distributed over a 3D volume, e.g. voxels by projecting aerial or floating images

Definitions

  • This invention relates to apparatus for displaying an image suspended in space, comprising: an object for display; a retroreflector being arranged to receive light from the object; a beamsplitter in a path for light from the object to the retroreflector, the beamsplitter being arranged at an oblique angle to the direction of propagation of the light such that it transmits part of the light and reflects part of the light, the light being either transmitted or reflected by the beamsplitter is received by the retroreflector and is reflected by it back to the beamsplitter, which either reflects or transmits part of this retroreflected light to form a real image suspended in space
  • apparatus as defined in the first paragraph above, characterised in that the apparatus further comprises a concave mirror being arranged between the beamsplitter and the retroreflector such that light from the beamsplitter is reflected by the concave mirror to the retroreflector which reflects it back via the concave mirror towards the beamsplitter in use.
  • a concave mirror between the beamsplitter and the retroreflector can improve viewability of the image by avoidance of reflections from the surfaces of one or more converging lenses.
  • the concave mirror is located such that it forms an image of the . given object or image in the plane of the retroreflector.
  • This can improve the resolution of the real image suspended in space significantly, and for example allows low cost bead retroreflectors to be used in high resolution displays. It can also increase the range of angles over which the image can be viewed.
  • the real image appears as a three dimensional image projected into or suspended in space.
  • Figure 1 shows an apparatus according to the invention for displaying a real image suspended in space.
  • the apparatus comprises an object (1) for display; a retroreflector (2) being arranged to receive light from the object; a beamsplitter (3) in a path for light from the object to the retroreflector, the beamsplitter being 2 arranged at an oblique angle to the direction of propagation (6) of the light such that it transmits part of the light (9), the light being transmitted by the beamsplitter is received by the retroreflector and is reflected by it back to the beamsplitter, which reflects part of this retroreflected light to form a real image (5) suspended in space.
  • the apparatus further comprises a concave mirror (4) being arranged between the beamsplitter (3) and the retroreflector (2) such that light from the beamsplitter is reflected by the concave mirror onto the retroreflector, which reflects it back to the concave mirror and then back towards the beamsplitter.
  • the object (1) comprises an illuminated object, although the object can comprise an image being displayed by a visual display unit.
  • the retroreflector comprises a sheet of bead type retroreflective material.
  • the retroreflective material may comprise a sheet of a corner cube retroreflecting material, or a triple mirror retroreflector, or other direction selective screen.
  • the invention will also function for the case in which light initially reflected by the beamsplitter is reflected by a concave mirror placed between the beamsplitter and a retroreflector positioned so as to retroreflect light arriving from the concave mirror.
  • two concave mirrors and two retroreflectors may be used such that one concave mirror and retroreflector combination receives light from the object initially transmitted by the beamsplitter and the other concave mirror and retroreflector combination receives light from the object which is initially reflected by the beamsplitter.
  • No alignment of the suspended images subsequently produced by each of the retroreflectors will be required since the retroreflectors will, by definition, return the light to the same locations. In this case the brightness of the suspended image subsequently produced will be increased by a factor of two.
  • a converging optical element such as the concave mirror is so advantageous is that contrary to simple theory a ray of light incident on a retroreflector will not be returned precisely along the direction from which it came because of diffraction effects, manufacturing tolerances, translational shifts, or other causes of imperfect retroreflection. As a result the incident ray becomes a narrow cone of light after retroreflection. If one places a converging optical element in the path of this cone of light it will behave as if it had originated at a point source, and the lens will bring the cone of light to a focus.
  • the concave mirror is positioned such that it 3 forms an image of the object at the surface of the retroreflector, then the point at which the same mirror will form an image of the point source from the cone of retroreflected light will coincide with the position of the original object, or where a beamsplitter diverts the light at the position of the suspended image.
  • the result of the presence of the concave mirror is a dramatic sharpening of the suspended image.
  • the improvement is such that bead retroreflectors (which do not retroreflect perfectly and so usually give rise to poor quality suspended images) can be used to form suspended images showing resolutions of TV quality.
  • a reduced area of retroreflector sheet is required.
  • the apparatus is preferably arranged such that the distance between the retroreflector and the concave mirror is selectable, or variable in use.

Abstract

Apparatus for displaying an image suspended in space comprises an object (1) for display, a retroreflector (2) receiving light from the object, a beamsplitter (3) in a path for light from the object to the retroreflector, and a concave mirror (4) between the beamsplitter and the retroreflector. The beamsplitter makes an oblique angle to the direction (6) of propagation of the light such that it transmits some light. Light from the beamsplitter is reflected by the mirror to the retroreflector which reflects it back via the mirror to the beamsplitter. This retroreflected light is reflected by the beamsplitter to form a real image (5) suspended in space. The use of a concave mirror improves viewability over apparatus including a converging lens because unwanted reflections from the surfaces of the lens are eliminated.

Description

1 APPARATUS FOR DISPLAYING AN IMAGE SUSPENDED IN SPACE
This invention relates to apparatus for displaying an image suspended in space, comprising: an object for display; a retroreflector being arranged to receive light from the object; a beamsplitter in a path for light from the object to the retroreflector, the beamsplitter being arranged at an oblique angle to the direction of propagation of the light such that it transmits part of the light and reflects part of the light, the light being either transmitted or reflected by the beamsplitter is received by the retroreflector and is reflected by it back to the beamsplitter, which either reflects or transmits part of this retroreflected light to form a real image suspended in space
A known display apparatus of this type is described in EP-A-0460873.
According to a first aspect of the present invention there is provided apparatus as defined in the first paragraph above, characterised in that the apparatus further comprises a concave mirror being arranged between the beamsplitter and the retroreflector such that light from the beamsplitter is reflected by the concave mirror to the retroreflector which reflects it back via the concave mirror towards the beamsplitter in use. The presence of a concave mirror between the beamsplitter and the retroreflector can improve viewability of the image by avoidance of reflections from the surfaces of one or more converging lenses.
Preferably, the concave mirror is located such that it forms an image of the . given object or image in the plane of the retroreflector. This can improve the resolution of the real image suspended in space significantly, and for example allows low cost bead retroreflectors to be used in high resolution displays. It can also increase the range of angles over which the image can be viewed.
If the object is three dimensional, then the real image appears as a three dimensional image projected into or suspended in space.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which :- Figure 1 shows a side view of a first embodiment.
Figure 1 shows an apparatus according to the invention for displaying a real image suspended in space. The apparatus comprises an object (1) for display; a retroreflector (2) being arranged to receive light from the object; a beamsplitter (3) in a path for light from the object to the retroreflector, the beamsplitter being 2 arranged at an oblique angle to the direction of propagation (6) of the light such that it transmits part of the light (9), the light being transmitted by the beamsplitter is received by the retroreflector and is reflected by it back to the beamsplitter, which reflects part of this retroreflected light to form a real image (5) suspended in space. The apparatus further comprises a concave mirror (4) being arranged between the beamsplitter (3) and the retroreflector (2) such that light from the beamsplitter is reflected by the concave mirror onto the retroreflector, which reflects it back to the concave mirror and then back towards the beamsplitter. In the present embodiment the object (1) comprises an illuminated object, although the object can comprise an image being displayed by a visual display unit. The retroreflector comprises a sheet of bead type retroreflective material. As an alternative, the retroreflective material may comprise a sheet of a corner cube retroreflecting material, or a triple mirror retroreflector, or other direction selective screen.
It will be realised by someone skilled in the art that the invention will also function for the case in which light initially reflected by the beamsplitter is reflected by a concave mirror placed between the beamsplitter and a retroreflector positioned so as to retroreflect light arriving from the concave mirror. Likewise two concave mirrors and two retroreflectors may be used such that one concave mirror and retroreflector combination receives light from the object initially transmitted by the beamsplitter and the other concave mirror and retroreflector combination receives light from the object which is initially reflected by the beamsplitter. No alignment of the suspended images subsequently produced by each of the retroreflectors will be required since the retroreflectors will, by definition, return the light to the same locations. In this case the brightness of the suspended image subsequently produced will be increased by a factor of two.
It is believed that the reason that the presence of a converging optical element such as the concave mirror is so advantageous is that contrary to simple theory a ray of light incident on a retroreflector will not be returned precisely along the direction from which it came because of diffraction effects, manufacturing tolerances, translational shifts, or other causes of imperfect retroreflection. As a result the incident ray becomes a narrow cone of light after retroreflection. If one places a converging optical element in the path of this cone of light it will behave as if it had originated at a point source, and the lens will bring the cone of light to a focus. If the concave mirror is positioned such that it 3 forms an image of the object at the surface of the retroreflector, then the point at which the same mirror will form an image of the point source from the cone of retroreflected light will coincide with the position of the original object, or where a beamsplitter diverts the light at the position of the suspended image. The result of the presence of the concave mirror is a dramatic sharpening of the suspended image. The improvement is such that bead retroreflectors (which do not retroreflect perfectly and so usually give rise to poor quality suspended images) can be used to form suspended images showing resolutions of TV quality. In addition, because light from the object is being focused onto the retroreflecting material a reduced area of retroreflector sheet is required. Hence smaller (cheaper) systems can be produced for a given viewing angle, or a greater viewing angle can be achieved with a given retroreflector area. Larger "seamless" images may be produced from a single retroreflective "tile" of a given size.
The apparatus is preferably arranged such that the distance between the retroreflector and the concave mirror is selectable, or variable in use.

Claims

4 CLAIMS
1. Apparatus for displaying an image suspended in space, comprising: an object for display; a retroreflector being arranged to receive light from the object; a beamsplitter in a path for light from the object to the retroreflector, the beamsplitter being arranged at an oblique angle to the direction of propagation of the light such that it transmits part of the light and reflects part of the light, the light being transmitted or reflected by the beamsplitter is received by the retroreflector and is reflected by it back to the beamsplitter, which either reflects or transmits part of this retroreflected light, to form a real image suspended in space, characterised by the apparatus further comprising a concave mirror being arranged between the beamsplitter and the retroreflector such that light from the beamsplitter is reflected by the concave mirror to the retroreflector which reflects it back via the concave mirror towards the beamsplitter in use.
2. Apparatus as claimed in any preceding claim in which the concave mirror is located such that it forms an image of the given object or image at the retroreflector.
3 Apparatus as claimed in any preceding claim in which a first retroreflector is provided to receive light being transmitted by the beamsplitter from the object and a further retroreflector is provided to receive light being reflected by the beamsplitter from the object, such that part of the light being reflected by both retroreflectors forms the real image suspended in space, a first and a further concave mirror being provided in the respective paths of light from the beamsplitter to said retroreflectors.
4. Apparatus as claimed in any preceding claim in which the retroreflector is a bead retroreflector.
5. Apparatus as claimed in any preceding claim in which the retroreflector is a triple mirror retroreflector.
6. Apparatus as claimed in any preceding claim in which the retroreflector is a corner-cube retroreflector.
7. Apparatus as claimed in any preceding claim in which the beamsplitter makes an angle of between 35 and 55 degrees to the direction of propagation of light from the object to the retroreflector.
8. Apparatus as claimed in any preceding claim in which the distance between the concave mirror and the retroreflector is selectable.
PCT/GB1999/000864 1998-04-09 1999-03-19 Apparatus for displaying an image suspended in space WO1999053359A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP99910549A EP1068554B1 (en) 1998-04-09 1999-03-19 Apparatus for displaying an image suspended in space
US09/647,889 US6421182B1 (en) 1998-04-09 1999-03-19 Apparatus for displaying an image suspended in space
CA002327412A CA2327412A1 (en) 1998-04-09 1999-03-19 Apparatus for displaying an image suspended in space
DE69900470T DE69900470T2 (en) 1998-04-09 1999-03-19 DEVICE FOR PRESENTING AN IMAGE FLOATING IN SPACE
JP2000543866A JP2002511601A (en) 1998-04-09 1999-03-19 A device for displaying images floating in space

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9807767A GB2336220B (en) 1998-04-09 1998-04-09 Apparatus for displaying an image suspended in space
GB9807767.0 1998-04-09

Publications (1)

Publication Number Publication Date
WO1999053359A1 true WO1999053359A1 (en) 1999-10-21

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Application Number Title Priority Date Filing Date
PCT/GB1999/000864 WO1999053359A1 (en) 1998-04-09 1999-03-19 Apparatus for displaying an image suspended in space

Country Status (8)

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US (1) US6421182B1 (en)
EP (1) EP1068554B1 (en)
JP (1) JP2002511601A (en)
CA (1) CA2327412A1 (en)
DE (1) DE69900470T2 (en)
ES (1) ES2168858T3 (en)
GB (1) GB2336220B (en)
WO (1) WO1999053359A1 (en)

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DE102008022011A1 (en) 2008-05-02 2009-11-05 Becker, Stefanie Device for virtual representation of a light source and use of this

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US6612701B2 (en) * 2001-08-20 2003-09-02 Optical Products Development Corporation Image enhancement in a real image projection system, using on-axis reflectors, at least one of which is aspheric in shape
US6798579B2 (en) * 1999-04-27 2004-09-28 Optical Products Development Corp. Real imaging system with reduced ghost imaging
US6935747B2 (en) * 1999-04-27 2005-08-30 Optical Products Development Image enhancement and aberration corrections in a small real image projection system
US20030035086A1 (en) * 2001-08-20 2003-02-20 Robinson Douglas L. Real image projection device incorporating e-mail register
DE102007006038B3 (en) * 2007-02-07 2008-08-28 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Autostereoscopic image display device for generating a floating real stereo image
US8042948B2 (en) * 2008-09-18 2011-10-25 Disney Enterprises, Inc. Apparatus that produces a three-dimensional image
US8029140B2 (en) 2008-09-18 2011-10-04 Disney Enterprises, Inc. Device to produce a floating image
JP2013113997A (en) * 2011-11-28 2013-06-10 Nikon Corp Three-dimensional image display device
US10302954B2 (en) * 2015-06-12 2019-05-28 Nippon Carbide Industries Co., Inc. Image display device
WO2018151220A1 (en) * 2017-02-15 2018-08-23 富士フイルム株式会社 Optical device
CN107632404A (en) * 2017-10-13 2018-01-26 北京眸合科技有限公司 Air suspension display system
JP2022001896A (en) * 2020-06-19 2022-01-06 京セラ株式会社 Aerial image projection device and movable body
CN114815010B (en) * 2022-05-15 2024-02-09 佛山科学技术学院 Lens array for 3D suspension imaging and device thereof

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JPS61132923A (en) * 1984-11-30 1986-06-20 Ricoh Co Ltd Image forming element
EP0460873A1 (en) * 1990-06-07 1991-12-11 THORN EMI plc Apparatus for displaying an image
WO1996003670A1 (en) * 1994-07-21 1996-02-08 Central Research Laboratories Limited An apparatus for displaying an image
US5629806A (en) * 1994-11-28 1997-05-13 Fergason; James L. Retro-reflector based private viewing system
WO1998037450A1 (en) * 1997-02-19 1998-08-27 Central Research Laboratories Limited Apparatus for displaying an image suspended in space

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GB2284680A (en) * 1993-12-13 1995-06-14 Central Research Lab Ltd Apparatus for displaying a suspended image
GB2287549B (en) * 1994-03-05 1997-05-28 Central Research Lab Ltd Apparatus for displaying a suspended image

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61132923A (en) * 1984-11-30 1986-06-20 Ricoh Co Ltd Image forming element
EP0460873A1 (en) * 1990-06-07 1991-12-11 THORN EMI plc Apparatus for displaying an image
WO1996003670A1 (en) * 1994-07-21 1996-02-08 Central Research Laboratories Limited An apparatus for displaying an image
US5629806A (en) * 1994-11-28 1997-05-13 Fergason; James L. Retro-reflector based private viewing system
WO1998037450A1 (en) * 1997-02-19 1998-08-27 Central Research Laboratories Limited Apparatus for displaying an image suspended in space

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Publication number Priority date Publication date Assignee Title
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Also Published As

Publication number Publication date
EP1068554A1 (en) 2001-01-17
CA2327412A1 (en) 1999-10-21
GB2336220A (en) 1999-10-13
JP2002511601A (en) 2002-04-16
EP1068554B1 (en) 2001-11-14
US6421182B1 (en) 2002-07-16
ES2168858T3 (en) 2002-06-16
GB9807767D0 (en) 1998-06-10
GB2336220B (en) 2001-11-14
DE69900470D1 (en) 2001-12-20
DE69900470T2 (en) 2002-06-06

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